APSS: Time Zones Can Offer a Major League Edge

BALTIMORE -- Baseball, a game of myriad statistics, now has a home-field circadian advantage.

Action Points

Explain to interested patients that it is well known that a change in time zones interferes with sleep and performance.

Note that this study suggests there is measurable effect of travel that can be seen in major league baseball.

Note that this study was published as an abstract and presented as a poster at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.

BALTIMORE, June 10 -- Baseball, a game of myriad statistics, now has a home-field circadian advantage.

An analysis of 24,133 major league baseball games over a 10-year period shows a distinct edge for the team with the circadian advantage, according to Christopher Winter, M.D., of Martha Jefferson Hospital in Charlottesville, Va.

A team has a circadian advantage when it's acclimated to the time zone it's playing in, but the other team is not, Dr. Winter said at SLEEP 2008, the annual meeting of the Associated Professional Sleep Societies.

For example, the New York Yankees flew last night from the east coast after a day game to Oakland to play the Athletics, who are just coming off a home series against Anaheim. So in tonight's game, at Oakland, the circadian advantage should have given a definite edge to the Athletics, but it didn't (the Yankees won 3-1).

That's because it takes a day to get over a one-time-zone change, Dr. Winter says, and three days to get over a transcontinental flight. It's not as simple as east coast versus west coast: "Where your team is from is somewhat meaningless," he said.

What matters is whether they're attuned to the local time, he said. By day three of their trip, the Yanks playing in Oakland are essentially a west coast team.

The three-hour advantage is relatively rare, but could be important in a tight playoff race. In 2004, for example, it occurred only 11 times but the team with the advantage won 10 games.

Of the 161 games over the 10 years where one team had a three-hour advantage over the other, the team with the edge won 97, or 60.2%.

Unlike home team advantage -- which is always in operation -- home time zone advantage is rare. Among the 24,133 games analyzed in this study, 19,075 were played with no circadian advantage for either team.

But in the remaining 5,046 games, the team with the advantage won 51.9% of the time -- 2,621 wins and 2,425 losses, a difference that was statistically significant at P=0.003.

In the games where the away team held the time zone edge, there was no difference statistically in win-loss ratio. Essentially, the home field advantage was eliminated, Dr. Winter said.

When teams did hold a time zone edge, the magnitude was important, Dr. Winter found, with a three-hour difference statistically better (P=0.036) than either a one- or two-hour difference.

Interestingly, the study found that teams who traveled west to east and held a circadian advantage had a better winning percentage (0.530) than those who had the edge but traveled the other way (0.509).

Dr. Winter said he grew up as a Brooklyn Dodger fan in a household that had supported the team since long before their controversial move west to Los Angeles. But if anything, he said, the analysis shows the Dodgers should win more games from their western base.

"The overall message is that disrupting sleep has significant impacts on performance," Dr. Winter said. While the benefits of the time zone advantage seen in his study appear small, he said, they can assume a huge importance when a playoff appearance hinges on the outcomes of one or two games.

The study is preliminary and the data need more analysis to try to discern what other factors might be involved, said Kenneth Wright, Ph.D., of the University of Colorado at Boulder, who was not involved in the study.

"Biologically, yes, it should make a difference, based on everything we know about how your clock system regulates how well you sleep and how well you perform, whether as an athlete or in a boardroom in an important business meeting," said Dr. Wright, a member of the conference's program committee.

But he said other things -- such as the time of day of the game or the meeting -- also play a part in performance and need to be analyzed.

The study was supported by Major League Baseball. Dr. Winter said he had no conflicts.

Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco

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